JPS6247196Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a dielectric heating device that heats an object by dielectric heating by supplying microwaves to a heating section of a waveguide and supplying an object to the heating section. .

Microwave dielectric heating devices are used in household microwave ovens, and are also widely used in industrial applications, such as in the vulcanization of rubber. The principle of dielectric heating is that the electrical dipoles of the dielectric material that is the object to be heated collide and generate heat as they are repeatedly reversed by a high-frequency electromagnetic field.This is different from heating the object from the outside. , which heats the object from inside. The thermal energy emitted per unit volume of the heated object per second is expressed by the following formula.

P=5/9εtanδ××(V/d) ² ×10 ^-12 [W/cm ² ] ε is the dielectric constant of the heated object, is the microwave frequency (Hz), tanδ is the dielectric loss tangent of the material, V is the voltage between the electrodes (volts), and d is the distance between the electrodes (cm).An industrial dielectric heating device is generally constructed as shown in FIG. That is, the microwave is transmitted from the microwave generator 11 to the isolator 1 through the waveguide 12.
The input and output are separated at 3 and further supplied to the heating section 14 through the waveguide 12. When the terminal end of the heating section 14 is short-circuited, it is necessary to provide a matching device 15 on the input side of the heating section 14, and when the terminal end of the heating section 14 is not short-circuited, the water load 16
absorbs leftover electromagnetic waves. In this case, the matching box 15 becomes unnecessary. The objects to be heated may be processed in batches within the heating section 14, or may be processed by passing through the heating section continuously like a belt conveyor.

The heating section 14 has a square wave waveguide structure, and for example, as shown in FIG. 2, the long side a of the square waveguide is connected to the short side b.
, and for the used wavelength λ, the long side a
is selected between λ and λ/2, and the short side b is smaller than λ/2. Excited in fundamental TE ₁₀ mode. In this case, as shown by a curve 17 in FIG. 2, the electric field distribution in a plane perpendicular to the tube axis is maximum at the center of the long side a.
Therefore, for example, as shown in FIG. 3A, the object to be heated 18 is moved inside the heating section 14 of the rectangular waveguide along its tube axis at the central position of the long side a to perform dielectric heating, or As shown in FIG. 3B, the object to be heated 18 is passed through the heating section 14 through the central part of the long side in a direction perpendicular to the tube axis, so that the object 18 is heated as it passes through the inside of the heating section 14.

For example, as shown in FIG. 4, the waveguide is repeatedly folded to form a heating section 14 so that the object to be heated passes through points with high electric field strength within the waveguide many times.
There is also one in which the waveguide 4 passes through each folded waveguide at right angles to the tube axis. Further, as shown in FIG. 5, the waveguides 14a to 14b are successively arranged adjacent to each other, and partition plates 19 are arranged in the longitudinal direction of these waveguides at regular intervals perpendicular to the tube axis.
Electromagnetic waves are propagated in opposite directions to those adjacent to a, 14b, 14c, and 14d as shown by arrows,
These comb-shaped waveguides fix the positions of the nodes and antinodes of the traveling wave in the tube, and the apparent wavelength in the tube is shortened, that is, the parts with strong electric field strength are arranged close together. There is also one in which the object to be heated 18 is passed through the heating section 14 in a direction perpendicular to the tube axis.

The heating section 14 shown in FIG. 4 has a relatively large loss at the bent portion of the waveguide, and therefore the length of the waveguide cannot be increased.

When the tan δ of the object to be heated 18 is small, taking advantage of the fact that tan δ increases when the object is heated, for example, as shown in FIG. lower hood 2
1, a heated gas 23 such as hot air or heated nitrogen gas is sent into the heating section 14, and the upper hood 22 collects the gas 23 that has passed through the heating section 14, heats it, and supplies it again to the lower hood 21. The temperature of the heated portion 18 may be increased by circulating the heated portion 18. The heating section 14 has many small holes through which hot air passes in the vertical direction. When performing such heating, heating section 1
The heated state of the object to be heated cannot be seen from the outside.

The purpose of this invention is to provide a dielectric heating device that can be installed in a relatively small installation space, can increase the length of the waveguide, and can heat efficiently.

FIGS. 7 and 8 show an embodiment of the dielectric heating device according to this invention, when applied to a standing waveform.
The heating section 14 is constructed by bending a rectangular waveguide 14a into a spiral shape of two or more stages. The short side b of this waveguide 14a is parallel to the central axis of the spiral,
The excitation mode for the waveguide 14a is TE ₁₀ , and therefore the magnetic field propagation surface is substantially perpendicular to the central axis of the helix. For example, microwaves are supplied and excited from the upper end 24 of the waveguide 14a, and the lower end 25 of the waveguide 14a is closed with a shorting plate (not shown).

A passage 2 through which the object to be heated passes approximately parallel to the central axis of the spiral at approximately the center of the long side a of the waveguide 14a.
6 is composed. The passage 26 is, for example, a waveguide 14a.
A slit along the tube axis of the waveguide 14a is formed at approximately the center of the long side, and the slits are sequentially provided facing each other on a line parallel to the axis of the spiral, and these slits form a passage 26 in the vertical direction. is configured. When the radius on the tube axis of the spiral waveguide 14a is R, 2πR is set to be an integral multiple of 1/2 of the tube wavelength λ, and therefore the standing wave generated at each stage of the spiral The positions of the nodes and antinodes of are made to match in the vertical direction. Strong heating is possible by forming passages 26 at each antinode position. However, if strong heating is not required, it is not necessary to select the radius R of the spiral as described above. The passage 26 may be formed along the entire circumference of the spiral. In this case, the heating section 14 has a structure in which a spiral inner part and an outer part of a waveguide divided into both sides along the tube axis are arranged concentrically.

If necessary, as shown in FIG. 7, a slit-shaped observation window 27 parallel to the helical axis can be formed on the circumferential surface of each spiral stage of the helical waveguide 14a. Such a peephole 27 can be provided at any location on the circumferential surface of the spiral, and may be provided not only at one but at a plurality of locations. A λ/4 stub can be attached to the outside of each peephole 27 to prevent electromagnetic waves from leaking from the peephole 27. When heating an object with heated gas, for example, an air outlet 28 projecting by a quarter wavelength is provided on the circumferential surface of the lower end of the spiral waveguide 14a, and hot air or the like is directed from this air outlet 28 into the waveguide 14a. It can be made to infuse into the air.

This spiral waveguide can also have a comb-shaped configuration, that is, a traveling waveform. For example, as shown in FIG. 9, partition plates 19 are arranged in a direction perpendicular to the tube axis of the helical waveguide 14a, that is, in a radial direction with respect to the helical axis, along the tube axis. The corresponding partition plates 19 are arranged on the same line in the direction of the helical axis. That is, by providing the partition plates 19 at the same angular position, the heating section 14 of the comb-shaped waveguide is constructed. In order to perform external heating when electromagnetic waves are used as traveling waveforms, for example, a spiral waveguide 14a is used.
A slit-shaped ventilation hole 29 is provided on the inner peripheral surface of each partition plate 1.
A slit-like exhaust hole 31 is formed in the outer peripheral surface of the spiral waveguide 14a in correspondence with these, and a slit-like exhaust hole 31 is formed in the outer circumferential surface of the spiral waveguide 14a. If hot air is sent inside, the hot air coming out of the exhaust hole 31 is collected through a cylindrical recovery cylinder 32 provided concentrically outside the heating part 14, heated, and then supplied to the inner peripheral cylinder again. good.

The above-mentioned heating section 14 is created by, for example, the spiral inner peripheral wall 33 of the spiral waveguide 14a in FIG.
The spiral wall 34 and the spiral wall 34 may be integrally made by machining a casting made of copper alloy or aluminum, and the cylindrical outer circumferential wall 35 may be inserted into the outside thereof. Furthermore, as shown in FIG. 10, by forming a part of the outer cylindrical peripheral wall as a door portion 36 that can be opened and closed about an axis 39 parallel to the axis, the heating section 14 can be opened and closed before use. Preparation and cleaning can be done easily. In addition, for disassembly and assembly, for example, as shown in FIG. 11, the cylindrical surface 37 that connects the area with the maximum electrolytic strength is divided into two inner and outer cylindrical sections, or the left and right sections are separated by a vertical surface 38 including the axis. It may be divided into The waveguide 14 may be bent into a spiral shape not only when one stage thereof is circular, but may also be bent into an elliptical or rectangular spiral shape. Further, two of such spirally bent waveguides may be provided coaxially in double or even in multiples.

As mentioned above, in the dielectric heating device according to this invention, the waveguide 14a is bent into a spiral shape, so there is little loss of microwaves propagating along this, and the entire length of the waveguide 14a is reduced. Since the waveguides 14a are bent so as to be stacked, the installation space is small.
It is particularly useful when heating objects to be heated by passing them in the vertical direction, and is useful for continuous heating of long bands, cloth, paper, tape, seaweed, threads, strings, etc.

In the case of the standing waveform shown in FIG. 7, the waveguide 14a
It is easy to heat the tube by blowing hot air along the axis of the tube, and the inside can be observed from any position on the outer circumferential surface.

[Brief explanation of the drawing]

Figure 1 shows the general configuration of an industrial dielectric heating device, Figure 2 shows the electric field distribution in the simplest form of the heating part, and Figure 3 shows the relationship between the heating part and the object to be heated. 4 and 5 are views showing a conventional heating section, FIG. 6 is a front view showing a state in which external heating is applied to the conventional heating section, and FIG. 7 is a dielectric heating device according to this invention. 8 is a plan view of FIG. 7, FIG. 9 is a perspective view of another example of the heating section of the dielectric heating device according to this invention, and FIG. 10 is a perspective view of the heating section of the dielectric heating device according to the invention. FIG. 11 is a perspective view showing still another example, and FIG. 11 is a perspective view showing an example in which the heating section is divided into two. 11...Microwave generator, 12...Waveguide,
14...Heating part, 14a...Spirally bent waveguide, 24...Microwave supply end, 26...
Passage of the object to be heated, 27...observation window, 28...hot air outlet.

Claims (1)

[Scope of utility model registration request] In a dielectric heating device that supplies microwaves to a heating section of a waveguide and passes an object through the heating section to dielectrically heat the object, the rectangular waveguide has its short side aligned with the central axis. The heating section is formed by bending two or more substantially parallel steps into a spiral, and the heating section is excited by microwaves in the TE ₁₀ mode, and the microwave magnetic field propagation surface is aligned with the central axis of the spiral. A dielectric device characterized in that a passage is formed that is substantially perpendicular to the waveguide, and allows the object to be heated to pass through the heating section substantially parallel to the central axis of the spiral at a substantially central position of the long side of the waveguide. heating device.